Over the years considerable work has been devoted to additives for controlling (preventing or reducing) deposit formation in the fuel induction systems of spark-ignition internal combustion engines. In particular, additives that can effectively control intake valve deposits represent the focal point of considerable research activities in the field and despite these efforts, further improvements are desired.
U.S. Pat. No. 4,231,759 (Udelhofen et al.) discloses liquid hydrocarbon fuels containing high molecular weight Mannich detergents and optionally, a non-volatile hydrocarbon carrier fluid. Preferred carrier fluids include polybutene and polypropylene. This reference fails to teach the use of polybutenes having a narrow molecular weight distribution or the advantages obtained by said use.
U.S. Pat. No. 5,514,190 (Cunningham et al.) discloses gasoline compositions containing Mannich detergents, poly (oxyalkylene) carbamates and poly (oxyalkylene) alcohols. These compositions may additionally contain hydrocarbon diluents, solvents or carriers including polymers of lower hydrocarbons such as polypropylene, polyisobutylene and ethylene-1-olefin copolymers. This reference fails to teach the use of polybutenes having a narrow molecular weight distribution or the advantages obtained by said use.
U.S. Pat. No. 5,634,951 (Colucci et al.) discloses gasoline compositions containing Mannich detergents. This patent teaches that carrier fluids, including liquid polyalkenes, may be added to the compositions. This reference fails to teach the use of polybutenes having a narrow molecular weight distribution or the advantages obtained by said use.